1. Field of the Invention
The present invention relates to a tool holder for a chip suction device, and specifically to improvement in suction of chip in a machining atmosphere and in loadability with respect to a spindle.
2. Description of the Related Art
There is a chip suction device that includes an external suction-type suction path provided so as to pass through the outside of a tool holder and a spindle. In a case where this type of external suction path is provided, when the tool holder is loaded to the spindle, there is a need to connect a suction passage on the tool holder side and a suction passage on the spindle side in an air-tight state. In this case, there is a problem that the connection is not securely conducted if there remains a chip in a connection portion between the both passages.
Accordingly, in Japanese Patent Publication No. 3055019, a part on a tool holder side and a part on a spindle side of a suction passage are placed to face each other with a gap provided therebetween, in which either of the parts is formed so that it can be expanded/contracted to be deformed, and it is configured that when a value of suction negative pressure becomes a predetermined value or greater, the both parts are closely brought into contact with each other. Accordingly, by sucking a chip remained in a connection portion at a time of starting suction, it is possible to securely connect the both parts by preventing the chip from being sandwiched between the both parts.